1. Field of the Invention
This invention relates to devices for inflating balloons or the like, particularly medical devices for inflating the balloons of catheters.
2. Description of the Prior Art
Many catheters currently in use in the vascular system have balloons located at their distal end. Angioplasty catheters, for example, have such balloons which are inflated within a plaque-containing stenosis to reform the stenosis to conform to the artery wall.
Angioplasty procedures can be painful to the patient if inflation lasts a long time so separate stopwatches which require separate handling are now frequently used in conjunction with the catheter to measure the length of inflation.
Special devices for inflating the balloon with a liquid such as saline or contrast media are also well known in the art. Originally, syringes were used for this purpose, and more sophisticated syringe-containing inflation devices have recently developed.
In order to control the amount of liquid (usually contrast media) injected into the balloon and obtain optimum inflation without balloon rupture, it has been found advisable to control the pressure input to the balloon. Devices which limit the amount of pressure in the inflation are disclosed in U.S. Pat. Nos. 4,795,431 and 4,865,587, both issued to Walling. Devices containing apparently removable pressure gauges external to the housing are shown in U.S. Pat. Nos. 4,743,230, 4,723,938, 4,758,223, and 4,919,121 issued to Nordquest, Goodin, Rydell and Rydell. However, it is highly desirable to include the pressure gauge in one, disposable unit with the inflation device, for convenience of the user, and avoid lengthy set-up procedures and the ordering of multiple devices.
Typical pressure gauges currently used with inflation devices are gauges based on Bourdon tubes. A Bourdon tube, somewhat flexible, and empty of liquid in the absence of a pressure reading, accesses a fluid-containing neck in the gauge which in turn accesses the channel in the inflation device delivering contrast media to the catheter. Upon pressure buildup, contrast media fills the neck and the tube, and compressing the air in the tube to change the tube's position so that a lever attached at the far end adjusts the position of the pressure gauge pointer. In the process, the contrast media in contact with the gauge, in particular the lead in the solder, becomes discolored and may well be toxic, such that a rupture in the balloon which leaks contrast media into the vasculature is potentially dangerous.
Using an externally-located, reusable (rather than disposable) pressure gauge and attempting to solve a different problem, i.e, the necessity of resterilizing an inflation device before re-use because the contrast media has come in contact with an external unsterilized pressure gauge, Reilly, in U.S. Pat. No. 4,370,982, discloses a multi-barrel inflation device attached to an external pressure gauge in which pressure measurement is based on axial movement of a barrel relative to the housing rather than direct pressure of the inflation fluid on the pressure gauge. It thus isolates the inflation fluid from the pressure gauge. The device, however, is complex, having a number of moving parts and an external pressure gauge, and thus may be expensive and cumbersome to manufacture and requires assembly with the pressure gauge before use.
According to Reilly in the Background of the Invention section of U.S. Pat. No. 4,370,982, it was previously known to interpose a T-fitting between the syringe of the inflation device and the catheter by interposing a gauge using a "separate pressure sensing member or disposable diaphragm positioned between the delivery end of the syringe and the balloon. One end of the diaphragm is contacted by the media fluid entering the balloon. While not admitting that this disclosure is enabling, it appears clear that a separate, disposable diaphragm (i.e. a disk) would have been used to separate the gauge from the fluid. In addition, the use of both a separate, nondisposable pressure gauge and the separate disposable diaphragm would have required special parts and special assembly of the device prior to use.
It thus would be desirable to provide a single-unit, already assembled, inflation device which avoids inflation fluid contamination by the pressure gauge. It would further be desirable to provide an inflation device which can be conveniently handled with a timer such as a stopwatch.